The invention is based on a fuel injection pump as revealed hereinafter. In a known fuel injection pump of this type, the control of the pressure exerted upon the control piston is effected with the aid of a pressure valve, the closing member of which is a ball and is stressed by a spring, the initial stress of which is variable in accordance with the ambient pressure. This embodiment has the disadvantage that upon the opening of the cross section closed by the ball pressure, fluctuations occur particularly at small flowthrough quantities, which affect the precise control of the pressure acting upon the control piston.